I would suggest finding a BIOS update that supports beyond the 8.4GB Limit then.. That is the easiest solution....

However if you are unable to do that... try out this suggested solution.
Source: http://www.microsense.com/Beyond-84.htm

2. Load software on the system that links into the BIOS to add the interrupt 13 support. There are several vendors that offer software for this purpose. Ontrack's Disk Manager for IBM (the diskette version 1.66K) can be downloaded at no charge from the following web site: http://service.boulder.ibm.com/stora...tech/dm955.exe